This invention relates to a flat display panel that may be a flat fluorescent or phosphorescent display panel, a flat gas discharge display panel, or a flat plasma display panel, and comprises as a part of a hermetically sealed envelope a planar substrate of an insulating material, such as glass or ceramic. The display panel is for use together with an external circuit for making the panel display a selected one of a plurality of displays. A display, of course may comprise a plurality of numerals, letters, and symbols.
A display panel of the type described comprises a plurality of electrodes for the plurality of displays in a space enclosed within the envelope. It is assumed without loss of generality that the display panel is for plural digit numerals. The substrate has an internal surface facing the space. The electrodes comprise segmented electrodes either on the internal surface or in indentation formed in the substrate in a substantially figure-eight configuration for each digit. If the display panel is a fluorescent display panel the electrodes further comprise one or more hot cathodes in front of the segmented electrodes and grids for the respective digits between the cathodes and the segmented electrodes. The cathodes are held by a pair of metal blocks fixedly attached to the substrate. The grids are supported by similar blocks. The blocks are called conductive end pieces herein. Terminals or lead wires are connected to the respective end pieces and led out of the space.
In general, further terminals, equal in number to the segmented electrodes for each digit, are connected to all segmented electrodes and extended outwardly of the envelope. Although no specific metal blocks are used to connect the terminals to the segmented electrodes, those ends of the terminals which are brought into contact with the segmented electrodes may be called conductive end pieces for convenience of description. These terminals extend at least partly along the internal surface. If the display panel is a gas discharge display panel, the electrodes further comprise transparent electrodes opposing the segmented electrodes of the respective digits with the space interposed therebetween. Connection means are conductively attached to all electrodes and disconnectively connected to the external circuit when the display panel is to be put into operation. The connection means includes terminals or leads conductively attached to conductive end pieces for the segmented electrodes and extended along the internal surface and through the envelope. Besides the segmented electrodes, the end pieces for the cathodes and grids may be made integral with the respective terminals. Each terminal extending at least parly along the internal surface generally consists of two portions, respectively deemed herein a terminal member and a connection piece.
In one type of the display panels, the terminal members are manufactured simultaneously and integrally with the connection pieces by applying silver paste onto the internal surface and its extension by the use of printing techniques. A display panel of this type has been objectionable with respect to its reliability because short circuit occur between the terminal members due to migration of silver when electric power is supplied to the terminals from the external circuit in a highly moist atmosphere. In another type of the display panels, the terminal members are rod-shaped leads of a metal, such as "426 Alloy", capable of being hermetically sealed in a mass of frit glass. In order to be sealed in the frit glass mass, the rod-shaped terminal members have to be thin so as to be better named "strip-shaped" leads or terminal members. When the number of the terminals are relatively large as in the case of a multi-digit display panel, the terminal members have to be as thin as 0.1-0.2 mm. In any event, it has been inevitable that the terminal members are defective in their mechanical strength. Furthermore, the "426 Alloy" is expensive. It has consequently been unavoidable that the display panels of the latter type are high-priced even when the substrates are made of glass to reduce the price.